Integrated chips are formed by complex fabrication processes that operate upon a semiconductor substrate with a plurality of steps performed by different processing tools. During such fabrication processes, contact between an integrated chip and the outside world is minimized to reduce contaminants that come into contact with the integrated chip and to thereby improve yield.
For example, integrated chips are fabricated in clean rooms that have low levels of contaminant particles (e.g., dust) that could be harmful to an integrated chip. Similarly, human contact with an integrated chip is minimized during fabrication processes by using wafer transfer robots to transfer semiconductor substrates from one location to another (e.g., between a wafer cassette and a processing tool, or vice versa).